Your calcium at 560 ppm is the most urgent problem here.

Critical Issues

Your calcium at 560 ppm is the most urgent problem here. Normal reef targets sit around 380-450 ppm, and at 560 you are well above that range. Elevated calcium at this level can trigger spontaneous precipitation, where calcium and carbonate bond and crash out of the water column as a chalky precipitate. This event simultaneously drives calcium and alkalinity down sharply and rapidly, and it can coat pump impellers, heater elements, and coral tissue. Your KH at 10 dKH is actually within a reasonable range (most reefs target 8-12 dKH), so alkalinity is not the primary offender here.

The combination of very high calcium with moderate alkalinity is chemically unstable. Precipitation risk increases significantly once calcium x alkalinity ion product climbs above roughly 500,000 (using ppm x meq/L), and your numbers are pushing into that territory.

Secondary Concerns

• Nitrate at 15 ppm is not dangerous but is on the higher side for a reef. SPS corals prefer under 5 ppm, and even LPS and soft corals do better below 10 ppm. This is worth addressing steadily through export methods.
• Temperature at 75 F is on the cooler end for a reef. A target of 77-79 F is more typical and stable for most reef inhabitants.
• pH at 8.1 is acceptable, though 8.2-8.3 is the conventional reef target. Not urgent, but worth noting.

Priority Actions

1. Stop all calcium dosing immediately. Do not add two-part, kalkwasser, calcium chloride, or any calcium-containing supplement until your levels normalize. This is the single most important step.
2. Identify the source of excess calcium. The most common causes are overdosing two-part solution with unequal parts (adding too much Part A relative to Part B), overusing kalkwasser, or miscalibrated dosing pumps. Check your dosing logs and equipment.
3. Do not attempt to lower calcium with large or aggressive water changes all at once. Sudden chemistry swings stress corals. Instead, perform a series of moderate water changes (10-15% weekly) using properly mixed saltwater that hits target parameters (calcium 420-430 ppm, alkalinity 8-9 dKH). This will dilute calcium gradually and safely.
4. Verify your test kit accuracy. A reading of 560 ppm is high enough that it is worth cross-checking with a second kit or an ICP test before acting aggressively. Reagent test kits can drift or give false highs with aged reagents.
5. Once calcium drops into the 420-440 ppm range, reintroduce dosing carefully and in balanced amounts, testing every 2-3 days until stable.

Watch Closely

• Test calcium every 2-3 days while it is this elevated and during your correction period. You want to catch any rapid drop that might indicate precipitation is occurring.
• Test alkalinity alongside calcium at each measurement. If KH starts falling sharply without explanation, precipitation may have begun. Act on that immediately with water changes.
• Retest nitrate in 2 weeks after reviewing your feeding and export methods to confirm it is trending down, not up.